1. Field of the Invention
The present invention relates to devices for preventing out of control acceleration in machines which are powered by internal combustion engines. More particularly, the present invention relates to an improved apparatus for monitoring the position of a carburetor piston valve in an internal combustion engine and a control circuit which shuts off the engine if the piston valve becomes stuck in an open position.
2. Description of the Prior Art 15 Carburetors for internal combustion engines commonly utilize piston valves to control the flow of fuel thereto prior to mixing the fuel with incoming air. Piston valves are controlled via a linkage connected to a throttle which is manipulated by an operator, and may be positioned for sliding movement within the carburetor body itself. In this way, the operator controls the supply of fuel to the carburetor, intake manifold and ultimately the combustion chambers of the engine itself.
One danger that is present in such arrangements is the runaway, uncontrolled engine speed that may result should the piston valve become stuck in its open position.
FIGS. 1 and 2 depict one system that has been commercially available for preventing such a runaway engine condition. In this system 10, a carburetor body 12 is provided with an outwardly protruding switch receiving socket 14, which has an inner bore that is at least partially threaded. A switch unit 16 having a threaded nipple 18 is screwed into socket 14. In order to monitor the movement of the piston valve 20, the piston valve is provided with a slide having a ramp 22 defined in a side surface thereof. A plunger 26 having a plastic end 24 is biased toward the ramp 22 to connect and disconnect switch 16. Switch 16 is connected to an ignition system by means of a connector 36.
Although it was somewhat effective in preventing runaway engine speeds, the above-described system had several disadvantages which became problematic in actual use. One such disadvantage was that wear on plastic end portion 24 and ramp 22 resulting from repeated use caused the switch activation point to change relative to the position of the piston valve. In addition, despite the provision of a relatively complicated and expensive system of seals, it was possible for gas and oil to leak from the carburetor into socket 14. Such seals substantially increased the complexity and cost of the switch. The added complexity of the switches further increased contact resistance, which causes spark plug fouling on engines which use capacitive discharge ignition systems.
A further disadvantage of the above-described system was that the added bulk created by socket 14 hindered efforts to reduce the size and weight of the engine.
Accordingly, it is clear that there has existed a long and unfilled need in the prior art for an improved piston valve detector device which has a constant point of actuation, does not allow fluids to leak from the carburetor and does not appreciably increase the bulk and weight of the carburetor assembly.